U.S. patent application number 17/347965 was filed with the patent office on 2022-05-05 for power generation apparatus and power generation method.
This patent application is currently assigned to KABUSHIKI KAISHA TOYOTA CHUO KENKYUSHO. The applicant listed for this patent is KABUSHIKI KAISHA TOYOTA CHUO KENKYUSHO. Invention is credited to Kazuma HIBI, Yasushi IWATA, Hiroshi KAWAHARA, Takuma MINOURA, Jun YAOKAWA.
Application Number | 20220140356 17/347965 |
Document ID | / |
Family ID | 1000005706411 |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220140356 |
Kind Code |
A1 |
YAOKAWA; Jun ; et
al. |
May 5, 2022 |
POWER GENERATION APPARATUS AND POWER GENERATION METHOD
Abstract
An object provides a power generation apparatus performing the
purification of an Al alloy melt using scrap as raw material. A
power generation apparatus includes: a container body with aluminum
alloy melt and molten salt in a liquid junction with the aluminum
alloy melt; an anode which is in contact with the aluminum alloy
melt; and a cathode which is in contact with the molten salt. DC
power is obtained from between the anode and the cathode by an
anode reaction on the aluminum alloy melt side and a cathode
reaction on the molten salt side. When the aluminum alloy melt and
the molten salt are separated by a separator allowing ionic
conduction between the aluminum alloy melt and molten salt, the
power generation efficiency is enhanced. The amount of a reactant
in the Al alloy melt is monitored by measuring the electrical
quantity associated with the power generation.
Inventors: |
YAOKAWA; Jun; (Nagakute-shi,
JP) ; HIBI; Kazuma; (Nagakute-shi, JP) ;
MINOURA; Takuma; (Nagakute-shi, JP) ; KAWAHARA;
Hiroshi; (Nagakute-shi, JP) ; IWATA; Yasushi;
(Nagakute-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOYOTA CHUO KENKYUSHO |
Nagakute-shi |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOYOTA CHUO
KENKYUSHO
Nagakute-shi
JP
|
Family ID: |
1000005706411 |
Appl. No.: |
17/347965 |
Filed: |
June 15, 2021 |
Current U.S.
Class: |
429/90 |
Current CPC
Class: |
H01M 6/50 20130101; C25C
3/24 20130101; H01M 6/14 20130101 |
International
Class: |
H01M 6/14 20060101
H01M006/14; H01M 6/50 20060101 H01M006/50; C25C 3/24 20060101
C25C003/24 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 2, 2020 |
JP |
2020-183395 |
Claims
1. A power generation apparatus comprising: a container body
containing an aluminum alloy melt and a molten salt that is in a
liquid junction with the aluminum alloy melt; an anode at least a
part of which is in contact with the aluminum alloy melt; and a
cathode at least a part of which is in contact with the molten
salt, wherein DC power is obtained from between the anode and the
cathode by an anode reaction on the aluminum alloy melt side and a
cathode reaction on the molten salt side.
2. The power generation apparatus according to claim 1, further
comprising a separator that separates the aluminum alloy melt and
the molten salt from each other while allowing ionic conduction
between the aluminum alloy melt and the molten salt.
3. The power generation apparatus according to claim 1, wherein the
anode or the cathode is electrically insulated from the molten salt
or the aluminum alloy melt.
4. The power generation apparatus according to claim 1, wherein the
cathode is provided with a supply means that supplies a raw
material to a periphery of the cathode, the raw material causing
the cathode reaction.
5. The power generation apparatus according to claim 1, further
comprising a monitoring means that, based on an amount of
energization between the anode and the cathode, perceives an amount
of a reactant caused by the anode reaction and/or the cathode
reaction.
6. The power generation apparatus according to claim 1, wherein the
power generation apparatus serves also as a melt processing
apparatus that performs removal or concentration adjustment of an
element contained in the aluminum alloy melt.
7. A power generation method comprising: preparing an aluminum
alloy melt and a molten salt that are in a liquid junction with
each other; and individually providing respective electrodes that
are in contact with the aluminum alloy melt and the molten salt,
wherein DC power is obtained by an anode reaction on the aluminum
alloy melt side and a cathode reaction on the molten salt side.
8. The power generation method according to claim 7, wherein the
molten salt contains a nobler metal element than Al.
9. The power generation method according to claim 8, wherein the
nobler metal element is one or more of Cu, Zn, or Mn.
10. The power generation method according to claim 8, wherein the
nobler metal element is supplied as an oxide or a halide to the
molten salt.
11. The power generation method according to claim 7, wherein the
molten salt is composed of a halide.
12. The power generation method according to claim 7, wherein at
least a part of a raw material of the aluminum alloy melt is
scrap.
13. The power generation method according to claim 7, wherein the
power generation method serves also as a purification method of
removing impurities from the aluminum alloy melt.
Description
TECHNICAL FIELD
[0001] The present invention relates to an apparatus that performs
power generation using an electrochemical reaction and relates also
to relevant techniques.
BACKGROUND ART
[0002] There are various principles and schemes for power
generation that generates electrical power essential for industrial
activities, daily life, etc. For example, power generation is
performed by power generators (electric motors) using
electromagnetic induction as well as physical batteries using a
photovoltaic effect, a Seebeck effect, or the like, chemical
batteries using an electrochemical reaction, etc.
[0003] Among these, chemical batteries convert chemical energy
changes of substances that occur with chemical reactions (such as
redox reactions) into DC power to perform efficient power
generation. Chemical batteries include primary batteries and
secondary batteries that contain a certain amount of active
substances (active materials) and fuel batteries that can be
replenished (supplied) with active substances.
PRIOR ART DOCUMENTS
Patent Documents
[0004] [Patent Document 1] U.S. Pat. No. 4,097,270B [0005] [Patent
Document 2] JP2007-154268A [0006] [Patent Document 3] JP2008-50637A
[0007] [Patent Document 4] JP2011-168830A
Non-Patent Documents
[0007] [0008] [Non-Patent Document 1] Journal of Japan Institute of
Light Metals, vol. 33 (1983), pp. 243-248 [0009] [Non-Patent
Document 2] Journal of Japan Institute of Light Metals, vol. 54
(2004), pp. 75-81
SUMMARY OF INVENTION
Technical Problem
[0010] Thus, various types of chemical batteries have been put into
practical use, but at present, there is not found any specific
proposal for power generation using an aluminum alloy melt. The
present invention has been made in view of such circumstances, and
an object of the present invention is to provide a novel power
generation apparatus and relevant techniques using an aluminum
alloy melt.
[0011] With the heightened environmental awareness, not only the
use of lightweight aluminum-based members are promoted, but also
the promotion of reuse of the scrap is important. Many proposals
have been made regarding the recycling of aluminum-based scrap, and
relevant descriptions are found, for example, in the above
documents. Unsurprisingly, none of the documents describes
performing power generation in parallel to the recycling and
refining of aluminum (alloy) or the like.
Solution to Problem
[0012] As a result of intensive studies, the present inventors have
succeeded in power generation through preparing an aluminum alloy
melt and a molten salt that are in a liquid junction with each
other and using chemical reactions (anode-cathode reactions/redox
reactions) that occur in the aluminum alloy melt and the molten
salt. Developing this achievement, the present inventors have
accomplished the present invention, which will be described
hereinafter.
Power Generation Apparatus
[0013] (1) The present invention provides a power generation
apparatus comprising: a container body containing an aluminum alloy
melt and a molten salt that is in a liquid junction with the
aluminum alloy melt; an anode at least a part of which is in
contact with the aluminum alloy melt; and a cathode at least a part
of which is in contact with the molten salt. In this power
generation apparatus, DC power is obtained from between the anode
and the cathode by an anode reaction on the aluminum alloy melt
side and a cathode reaction on the molten salt side.
[0014] (2) According to the power generation apparatus of the
present invention, DC power can be obtained, which is output
between the anode provided on the aluminum alloy melt side and the
cathode provided on the molten salt side. The reasons for this are
considered as follows.
[0015] When the aluminum alloy melt (also simply referred to as an
"Al alloy melt/aluminum-based molten metal") and the molten salt
are in liquid junction with each other so as to be capable of ionic
conduction, the cathode reaction of a cathode active substance
(e.g., an elementary substance such as Cu, Zn, or Mn or its alloy
or compound) contained in the molten salt can occur along with the
anode reaction of an anode active substance (e.g., an elementary
substance such as Mg, Na, Li, or Al or its alloy or compound)
contained in the Al alloy melt.
[0016] When respective electrodes are provided on the Al alloy melt
side and the molten salt side, the chemical energy generated by
each reaction is taken out as electrical energy (electrical power)
from the Al alloy melt side electrode (anode) and the molten salt
side electrode (cathode).
[0017] Provided that the Al alloy melt and the molten salt are in a
liquid-junction state (state in which ionic conduction is possible)
and the active substances are present, each reaction can be
continued (sustained). That is, predetermined electromotive force
is output even after energization, and stable power generation can
be performed. Moreover, long-term power generation is possible by
replenishment/resupply or the like of the active substances.
Furthermore, when inexpensive scrap, oxide, or the like is used as
the raw material containing an active substance, the power
generation cost can be reduced.
[0018] The anode active substance element (including Al) in the Al
alloy melt is consumed by the power generation, and the
concentration change (including removal) may occur. The power
generation apparatus of the present invention can therefore be
considered also as a melt processing apparatus that performs
removal or adjustment of the concentration of an element contained
in the Al alloy melt. Additionally or alternatively, the melt
processing apparatus may be considered also as a purification
apparatus if the element to be removed or reduced in its
concentration is an impurity.
[0019] As a matter of course, it appears that the same applies to
the cathode active substance in the molten salt. That is, the
cathode active substance element in the molten salt is consumed by
the power generation, and the concentration change (including
precipitation or deposition) of the element may occur. The power
generation apparatus of the present invention can therefore be
considered also as a processing apparatus that performs the
concentration adjustment, precipitation or deposition, recovery, or
the like of an element contained in the molten salt. For example,
when an inexpensive compound (such as oxide or halide) is used as
the raw material for the cathode active substance, a noble metal
that is the cathode active substance can be precipitated or
deposited (isolated) and recovered.
Tower Generation Method
[0020] The present invention is perceived also as a power
generation method. For example, the present invention may provide a
power generation method comprising: preparing an aluminum alloy
melt and a molten salt that are in a liquid junction with each
other; and individually providing respective electrodes that are in
contact with the aluminum alloy melt and the molten salt. In this
power generation method, DC power is obtained by an anode reaction
on the aluminum alloy melt side and a cathode reaction on the
molten salt side.
Others
[0021] (1) In the present specification, the anode reaction is
referred to as "oxidation (reaction)," the cathode reaction is
referred to as "reduction (reaction)," and both are collectively
referred to as "redox (reaction)," as appropriate. The "oxidation"
and "reduction" as referred to in the present specification mean
reactions that involve the transfer of electrons and do not
necessarily mean the involvement of O in the reaction.
[0022] Unless otherwise stated, the concentration and composition
as referred to in the present specification are indicated by the
mass ratio (mass %) of an object (such as melt or molten salt) to
the whole. Mass % is simply indicated by "%" as appropriate.
"X-based" materials include not only an X alloy/compound that
contains X as the main component (content with respect to the whole
is more than 50%) but also the elementary substance of X. The Al
alloy melt usually contains 60% or more of Al in an embodiment or
75% or more of Al in another embodiment with respect to the melt as
a whole.
[0023] (2) Unless otherwise stated, a numerical range "x to y" as
referred to in the present specification includes the lower limit x
and the upper limit y. Any numerical value included in various
numerical values or numerical ranges described in the present
specification may be selected or extracted as a new lower or upper
limit, and any numerical range such as "a to b" can thereby be
newly provided using such a new lower or upper limit.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a schematic view illustrating an example of a
power generation apparatus.
[0025] FIG. 2A is a photograph showing an example of a cathode and
an encircling body.
[0026] FIG. 2B is an enlarged explanatory view of a part (part A)
of a porous container body.
[0027] FIG. 3 is a graph illustrating an example of changes over
time in the generated voltage, current, electrical quantity, and
electrical energy.
[0028] FIG. 4 is a scatter diagram illustrating the relationship
between the amount of reactants determined by chemical analysis of
the melt and the amount of reactants measured from the electrical
quantity.
[0029] FIG. 5 is a schematic diagram illustrating a modified
example of the power generation apparatus.
[0030] FIG. 6 is a standard formation free energy diagram of metal
oxides and metal chlorides at 660.degree. C.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0031] One or more features freely selected from the present
specification can be added to the above-described features of the
present invention. The content described in the present
specification can be features regarding a product even when the
content represents methodological features.
Al Alloy Melt
[0032] The Al alloy melt is not limited in the specific composition
of components, the type of a raw material used for preparing the
melt, or the like. Scrap of an Al-based member may be used as a raw
material for the Al alloy melt to promote the application and
regeneration.
[0033] When the Al alloy melt contains one or more types of metal
elements .alpha. (such as Mg, Na, and Li, for example) that are
less noble than Al, they can be raw materials (anode active
substances) for anode reactions (such as
.alpha..fwdarw..alpha..sup.2++2e.sup.- and
.alpha..fwdarw..alpha..sup.++e.sup.-). The metal elements (.alpha.)
are ionized to migrate into to the molten salt decreasing the
concentration in the Al alloy melt depending on the amount of power
generation.
[0034] Mg, which is a type of the metal elements (.alpha.), is a
typical alloy element of aluminum alloys (also simply referred to
as "Al alloys") and is contained in many Al alloys (such as 5000
series, 6000 series, and 7000 series). Na is contained in cryolite
(Na.sub.3AlF.sub.6) that is used when smelting aluminum from
alumina (Hall-Heroult method). The power generation apparatus
(method) of the present invention can therefore perform not only
the power generation but also refining and regeneration of Al alloy
as well as smelting of Al. When the Al alloy melt does not contain
a metal element a that is less noble than Al, Al is a raw material
(anode active substance) for the anode reaction
(Al.fwdarw.Al.sup.3++3e.sup.-).
[0035] The Al alloy melt may contain one or more types of metal
elements .beta. (such as Fe, Mn, Si, Cu, and Zn, for example) that
are nobler than Al. The metal elements .beta. cannot be anode
active substances, but are concentrated in the Al alloy melt with
the power generation. As a result, for example, Fe and Mn are
likely to form compounds by concentration, and they can be removed
from the Al alloy melt by sedimentation or the like or can reduce
the concentration in the Al alloy melt.
[0036] The Al alloy melt can also be perceived as a conductor
responsible for electron conduction. Additionally or alternatively,
when the Al alloy melt contains an anode active substance other
than Al, it can also be perceived as a current collector
(electrode). Additionally or alternatively, when Al itself is
considered as an anode active substance, the Al alloy melt can also
be perceived as a supply source for the anode active substance. The
Al alloy melt may be in a solid-liquid coexisting state
(semi-molten state). This also applies to the molten salt.
[0037] The "noble/less noble" metal element as referred to in the
present specification is determined based on the standard formation
free energy (see FIG. 6) in the molten salt in contact with the Al
alloy melt. As the absolute value of negative standard formation
free energy increases, the metal element is less noble. In FIG. 6,
representative metals (elementary substances) are arranged from the
left in the order of less noble state in the chloride molten salt.
The standard formation free energy not illustrated in FIG. 6 may be
obtained from a data collection or potential measurement.
Molten Salt
[0038] The molten salt serves as an electrolyte. The molten salt
(fused salt) is also not limited in the specific composition of
components, the type of a raw material used for preparing the
molten salt, or the like. As the molten salt, for example, a halide
salt, a carbonate, or the like can be used. When a halide (in
particular, chloride or bromide) is used, a stable molten salt can
be prepared at low cost.
[0039] More specifically, for example, the base material of a
molten salt may be a halide of a metal element (one or more of Ca,
Na, Li, Sr, K, Cs, Ba, and other similar elements) whose standard
formation free energy (see FIG. 6), which will be described later,
is smaller than that of Mg halides. In particular, halides of Na
and/or K are inexpensive and stable and therefore suitable as the
base material of a molten salt. The molten salt may be a single
type salt or may otherwise be a plurality of types of salts (mixed
salts). A plurality of halide salts can be combined thereby to
lower, for example, the melting point of the molten salt.
[0040] When the molten salt contains a metal element (.beta.) that
is nobler than Al, it can be a raw material (cathode active
substance) for a cathode reaction (such as
.beta..sup.2++2e.sup.-.fwdarw..beta. or
.beta..sup.++e.sup.-.fwdarw..beta.). The metal element (.beta.) can
be deposited on the cathode (or precipitated in the vicinity of the
cathode), for example, depending on the amount of power
generation.
[0041] The metal element (.beta.) is, for example, Cu, Sn, Fe, Zn,
Mn, or the like. The metal element (.beta.) is supplied, for
example, as an elementary substance, a compound, or the like to the
molten salt. When using a compound of the metal element (.beta.),
the raw material cost required for the power generation can be
reduced. Examples of such a compound include oxides and halides (in
particular, chlorides). In general, when using an oxide rather than
a halide, the raw material cost can be more reduced. Moreover, when
using an oxide of the metal element (.beta.), the element (such as
Mg) contained in the Al alloy melt can be easily removed as an
oxide (such as MgO).
[0042] Furthermore, the metal element (.beta.) may be preferably a
specific metal element (M) that is one or more of Cu, Zn, or Mn (in
particular, Cu). The standard formation free energy of an oxide of
the specific metal element is larger than or approximately the same
as the standard formation free energy of its halide (in particular,
a chloride) (see FIG. 6). The oxide (such as CuO, ZnO, or MnO) of
the specific metal element (M) is therefore easily decomposed in
the molten salt composed of the halide. As a result, the specific
metal element (M) is deposited on the cathode, for example, and O
can remove ions (such as Mg.sup.2+) that have migrated from the Al
alloy melt, as oxides. An example of the reaction is represented by
a reaction formula 1: MO+MgX.sub.2.fwdarw.MX.sub.2+MgO (X: halogen
element, in particular, Cl or Br).
[0043] MX.sub.2 in the molten salt reacts as in a reaction formula
2: MX.sub.2+Mg.fwdarw.M+MgX.sub.2, for example, and also serves as
an Mg removing material. It can be found from FIG. 6 that, in any
of the reaction formulas, the reaction is likely to proceed in a
stable direction in which the free energy difference is negative
(.DELTA.G<0), that is, from the left side to the right side. The
amount of Mg removed from the Al alloy melt varies depending on the
amount of oxide (MO) supplied (added) to the molten salt, but the
amount of MgX.sub.2 in the molten salt (Mg.sup.2+ concentration in
the molten salt) is approximately constant.
[0044] The standard formation free energy (also simply referred to
as "free energy") illustrated in FIG. 6 relies on Knacke O.,
Kubaschwski O., Hesselmann K., "Thermochemical Properties of
Inorganic Sub stances" (1991), SPRINGER-VERLAG. FIG. 6 illustrates
each free energy at 660.degree. C., but the tendency is the same as
that of each free energy at least at 660.degree. C. to 800.degree.
C.
Electrodes
(1) Current Collectors
[0045] The power generation apparatus of the present invention is
also considered as a type of a galvanic battery. Therefore, to
extract as the electrical energy the chemical energy released when
the anode active substance on the Al alloy melt side and the
cathode active substance on the molten salt side undergo a redox
reaction, the Al alloy melt side and the molten salt side may be
preferably provided with respective independent electrodes. That
is, it is preferred to independently provide an anode (a negative
electrode) on the Al alloy melt side and a cathode (a positive
electrode) on the molten salt side.
[0046] Each electrode may be preferably composed of a current
collector at least a part of which is in contact with the aluminum
alloy melt or molten salt. The current collector may be preferably
composed of a material that does not adversely affect the redox
reaction. For example, the current collector (electrode) can be a
graphite electrode (such as a graphite rod or a graphite plate)
that is excellent in the heat resistance and corrosion resistance
and is relatively inexpensive.
[0047] When a part of the anode passes through the molten salt, it
is preferred to provide a covering member or a covering layer on
the outer peripheral side of the anode to electrically insulate the
anode from the molten salt. When both are in a conductive
(short-circuited) state, a cathode reaction (deposition or
precipitation of the cathode active substance (such as Cu)) may
occur on or near a part of the anode to lower the power generation
efficiency. The material of the covering member or covering layer
is not limited, provided that the anode and the molten salt are
insulated from each other. As the material, for example, an
insulating material such as ceramics may be preferably used.
Likewise, when the cathode passes through the Al alloy melt, it is
preferred that both be electrically insulated from each other.
(2) Terminals
[0048] The electrodes (current collectors) can be used as output
terminals that are connected to an external circuit without any
modification. Fortunately, however, when output terminals are
provided separately from the electrodes, not only the connectivity
with the external circuit is improved, but also it is easy to
replace only a consumable electrode. Therefore, an anode terminal
that is linked to the anode and can be connected to an external
circuit and a cathode terminal that is linked to the cathode and
can be connected to the external circuit may be further provided.
Both terminals may be preferably composed of the same material
(metal).
(3) Supply Means
[0049] It is preferred to provide a supply means that supplies a
raw material causing the cathode reaction (raw material of the
cathode active substance) to the periphery of the cathode. The
supply means is, for example, a liquid-permeable enclosure or the
like provided around the cathode. This can concentrate the cathode
active substance around the cathode and enhance the power
generation efficiency. The supply means may be integrated with the
cathode or may otherwise be separate from the cathode.
Separator
[0050] In general, the Al alloy melt and the molten salt are
naturally in a two-layer (two-phase) state (the upper/lower layer
is determined by each density). Therefore, the power generation
apparatus of the present invention can be realized without
necessarily having a separator, unlike a battery using two types of
aqueous solutions as the electrolytic liquids. However, if the Al
alloy melt and the molten salt come into direct contact with each
other, precipitation of the cathode active substance due to the
redox reaction may occur in the vicinity of the contact interface
between the two. It is therefore preferred to provide a separator
that separates the aluminum alloy melt and the molten salt from
each other while allowing ionic conduction between the aluminum
alloy melt and the molten salt. This allows the stable power
generation to be efficiently performed.
[0051] The separator may be a partition wall extending in the
longitudinal direction (vertical direction) (simply referred to as
a "longitudinal wall") or may otherwise be a partition wall
extending in the lateral direction (horizontal direction) (simply
referred to as a "lateral wall"). When the separator is a
longitudinal wall, the supply, replenishment, or the like of the
raw materials can be performed from each of the upper surfaces of
the Al alloy melt and molten salt.
[0052] The separator may also serve as a container body that
contains the Al alloy melt or the molten salt. In this case, it
suffices that at least a part of the wall surface of the container
body is capable of ionic conduction.
[0053] The separator may be preferably composed of a porous body
having heat resistance. For example, an unglazed container body
such as a porous crucible can be used as the separator. As
illustrated in FIG. 2B, such a separator allows ions (including the
molten salt) to pass through, but does not allow the melt to pass
through.
Container Body
[0054] The Al alloy melt and the molten salt may be contained in
one container body or may otherwise be contained in respective
divided or independent container bodies. The container body may be
made of ceramics or metal. The Al alloy melt may be contained in a
porous container body capable of ionic conduction (passage), and
the above-described separator may be omitted.
Monitoring Means
[0055] The power generation apparatus of the present invention uses
the redox reaction (electron transfer at the electrodes), and
therefore the amount of energization (electrical quantity) between
the electrodes can be approximately proportional to the amount of a
reactant at each electrode (Faraday's law (electrolysis law). As
such, it is also possible to perceive (monitor) the amount of a
reactant on the Al alloy melt side or the molten salt side based on
the amount of energization. In this regard, the power generation
apparatus of the present invention may include a monitoring means
that, based on the amount of energization between the anode and the
cathode, perceives the amount of a reactant caused by the anode
reaction and/or the cathode reaction. The monitoring means may
comprise, for example, a calculation means for the amount of a
reactant and a display means for the calculated amount of the
reactant. The value to be monitored of a reactant may be the amount
of metal element (such as Mg) that is removed from/reduced in the
Al alloy melt side or may otherwise be the amount of metal element
(such as Cu) that is deposited or precipitated on the molten salt
side.
[0056] Calculation of the amount of a reactant is performed, for
example, as follows. Assuming that the amount of current in an
external circuit is I (A) and the energization time is t (sec), the
electrical quantity is represented by Q=It (C). Then, assuming that
the Faraday constant F is 96485 (C/mol), the molar mass is B (g),
and the ionic valence of a reactant is z, the amount of reactant is
obtained as m=BQ/zF (g)=BIt/zF (g).
[0057] When the voltage between the electrodes (between the
terminals) is E (V), the amount of power generation is presented by
P=EIt (J), and the amount of reactant is also obtained as m=BP/EzF
(g).
Examples
[0058] A power generation apparatus capable of power generation
using an Al alloy melt and a molten salt was manufactured, and the
applicability to power generation and the amount of reactants
caused by the power generation were evaluated. The present
invention will be described in more detail based on such a specific
example.
Tower Generation Apparatus
[0059] The outline of a power generation apparatus G manufactured
is schematically illustrated in FIG. 1. The power generation
apparatus G comprises an anode 11, an anode terminal 12, a cathode
21, a cathode terminal 22, an encircling body 23 (enclosure/supply
means), a porous container body 6 (separator), a heater 7, a
holding furnace 8, and a liquid bath 9 (container body). The power
generation apparatus G is connected to an external circuit, and the
external circuit is provided with an ammeter A, a voltmeter V, and
a switch SW.
[0060] The anode 11 and the cathode 21 are each composed of a
graphite current collector (graphite electrode). The anode terminal
12 attached to the upper end of the anode 11 and the cathode
terminal 22 attached to the upper end of the cathode 21 are
composed of copper. The encircling body 23 has a bottomed
cylindrical shape that covers the lower side of the cathode 21. The
cylindrical side surface of the encircling body 23 is provided with
a plurality of through holes (referred to as "liquid holes")
through which liquid can pass. The bottom portion of the encircling
body 23 and the lower end portion of the cathode 21 are integrated,
and both are electrically conductive. FIG. 2A shows an example of
such cathode 21 and encircling body 23. In the present example,
graphite electrodes having an outer diameter of .phi.5 mm were used
as the anode 11 and cathode 21.
[0061] The porous container body 6 has a bottomed tubular shape and
contains an Al alloy melt m1 (simply referred to as a "melt m1").
The porous container body 6 is composed of entirely porous ceramics
(unglazed ceramics). As illustrated in FIG. 2B, the porous
container body 6 does not allow the melt m1 itself to pass through,
but allows ions (e.g., Mg.sup.2) in the melt m1 and ions of a
molten salt m2 to pass through. In the present example, a porous
crucible (special refractory crucible made of
MgO/40.times.30.times.100 mm) available from NIKKATO CORPORATION
was used as the porous container body 6.
[0062] The heater 7 is of an electric heating type and provided
inside the holding furnace 8 composed of a heat insulating
material. The liquid bath 9 accommodates the porous container body
6, which contains the melt m1, and the molten salt m2 in which the
melt m1 is immersed. The temperature of the molten salt m2 in the
liquid bath 9 was maintained constant by the heater 7 and the
holding furnace 8. In the present example, a dense crucible (made
of alumina/SSA-H.cndot.B5) available from NIKKATO CORPORATION was
used as the liquid bath 9.
Experiments
[0063] Using the power generation apparatus G illustrated in FIG.
1, removal of the metal element (anode active substance) contained
in the melt m1 (purification or concentration adjustment of the Al
alloy melt) and deposition or precipitation of the metal element
(cathode active substance) added to the molten salt m2 was
performed in parallel to the power generation as follows.
1. Raw Materials
(1) Al Alloy Melt
[0064] Al--Mg alloy melt (melt m1) was prepared using commercially
available pure Al and pure Mg. At that time, the assumption was
made for a case of purifying the aluminum alloy melt through
removing Mg (impurities) from a raw melt obtained by melting the
scrap to be recycled.
[0065] The initial concentration of Mg (anode active substance)
with respect to the entire melt was 0.85% or 1.31%. In the present
example, unless otherwise stated, the concentration is indicated by
mass ratio (mass %). The amount of melt prepared was about 80 g or
about 100 g.
(2) Molten Salt
[0066] Using commercially available chloride (reagent), the molten
salt m2 of KCl-43% NaCl-1.4% MgCl was prepared.
(3) Cathode Active Substances
[0067] CuO, CuCl.sub.2, and CuCl were prepared as cathode active
substances (raw materials for power generation on the cathode
side). The ionic valence of Cu in CuO and CuCl.sub.2 is 2 while the
ionic valence of Cu in CuCl is 1. Each molar mass is CuO: 79.545,
CuCl.sub.2: 134.45, CuCl: 98.999. Therefore, in the case of CuO: 1
g, CuCl.sub.2: 1.7 g, and CuCl: 2.5 g, for example, the
electrochemical equivalents are approximately the same.
2. Power Generation
[0068] The heater 7 was operated with the switch SW turned off to
maintain the above-described melt m1 and molten salt m2 at
730.degree. C. An Al-0.85% Mg alloy melt was used as the melt
m1.
[0069] After that, the switch SW was turned on, and as an example,
CuCl.sub.2: 1.7 g was added to the encircling body 23. The changes
over time in the voltage E (V) and the current I (A) generated
after the addition were continuously measured. In addition, the
electrical quantity Q=It (C) and the amount of power generation
P=EIt (J) when the time t (s) elapsed since the addition of
CuCl.sub.2 were calculated. The results thus obtained are
collectively illustrated in FIG. 3.
[0070] As apparent from FIG. 3, it has been confirmed that the
power generation apparatus G can perform DC power generation with a
stable output (voltage E/current I). When the surface of the
cathode 21 was observed, Cu was deposited.
3. Amount of Reactants
[0071] Using the power generation apparatus G, power generation was
performed in the same manner under the conditions listed in Table
1. At that time, Al-1.31% Mg alloy melt (initial concentration) was
used as the melt m1. Either CuCl: 2.5 g, CuCl.sub.2: 1.7 g, or CuO:
2 g was added as the cathode active substance to the encircling
body 23 in the molten salt m2. The electrochemical equivalent ratio
is represented by CuCl:CuCl.sub.2:CuO=1:1:2.
[0072] Each Al alloy melt after the lapse of processing time as
listed in Table 1 was taken out and poured into a cylindrical mold
(stainless steel analysis mold). It was naturally cooled in the air
to obtain a disk-shaped casting. The chemical composition (Mg
concentration) was quantitatively analyzed using fluorescent X-ray
spectroscopy (XRF: X-Ray Fluorescence).
[0073] The reaction amount (analyzed value) of Mg associated with
the power generation was calculated from the amount of decrease in
Mg concentration obtained from this melt analysis and the initial
amount of melt. The results are also listed in Table 1. In
addition, the maximum reaction amount of Mg (theoretical value)
obtained stoichiometrically from the additive amount of the cathode
active substance and the reaction amount of Mg (calculated value)
calculated based on the Faraday's law from the electrical quantity
obtained by measuring the current are also listed in Table 1.
Furthermore, on the basis of the results listed in Table 1, the
relationship between the reaction amount of Mg determined by the
melt analysis and the reaction amount of Mg measured by the
electrical quantity is illustrated in FIG. 4.
[0074] As apparent from FIG. 4, it has been confirmed that the
reaction amount of Mg determined by the melt analysis and the
reaction amount of Mg measured by the electrical quantity are
approximately proportional to each other and in line with the
Faraday's law. It has thus been found that also in the present
example, the amount of reactants (such as the amount of Mg removed)
can be monitored by measuring the electrical quantity (amount of
energization, amount of power generation) (monitoring means).
[0075] The reason why the electrical quantity or the reaction
amount determined by the melt analysis is larger than the
theoretical value (maximum value) based on the additive amount
listed in Table 1 is that a part of Mg in the Al melt reacts with
the air and is consumed due to oxidation.
[0076] From the above, it has been confirmed that according to the
power generation apparatus (power generation method) of the present
invention, stable power generation can be performed using the Al
alloy melt, which contains the anode active substance, and the
molten salt, which contains the cathode active substance. It has
also been confirmed that the purification of the Al alloy melt
(including adjustment of the concentration of contained metal
elements) can be performed in parallel to the power generation.
Furthermore, it has also been confirmed that the amount of
reactants generated at that time can be monitored by measuring the
electrical quantity associated with the power generation.
Modification Example
[0077] FIG. 5 illustrates a power generation apparatus G1 in which
a part of the power generation apparatus G is modified. The
previously described members and the like are denoted by the same
reference numerals or characters, and the description thereof will
be omitted as appropriate.
[0078] The power generation apparatus G1 includes a porous plate 61
(separator) as substitute for the porous container body 6. The
porous plate 61 separates the melt m1 and the molten salt m2 into
two lower and upper layers, respectively. The porous plate 61 is
also composed of porous ceramics like the porous container body 6
(see FIG. 2B).
[0079] The lower-upper relationship between the melt m1 and the
molten salt m2 depends on their densities. Therefore, the melt m1
may be the upper layer. As illustrated in FIG. 5, when the melt m1
is the lower layer, it is preferred to provide an insulating tube
62 on the outer peripheral surface side of the anode 11 so that the
anode 11 does not come into contact with the molten salt m2. This
can prevent the cathode active substance (such as Cu.sup.2+)
contained in the molten salt m2 from being directly deposited on
the surface of the anode 11, and the power generation efficiency is
improved. The power generation itself is possible even when one or
both of the porous plate 61 and the insulating tube 62 are
absent.
TABLE-US-00001 TABLE 1 Conditions of power generation Reaction
amount of Mg (g) Amount of Cathode Calculated Analyzed Al--Mg
active substance Electrical Theoretical value value Sample alloy
melt Additive Processing quantity value based on measured by
determined by No. (g) Type amount (g) time (s) (C) additive amount
electrical quantity melt analysis 1 80.6 CuCl 2.5 2396.5 1659.7
0.307 0.405 0.387 2 100.2 CuCl.sub.2 1.7 925.5 644.2 0.307 0.218
0.160 3 100.0 2227.5 1488.3 0.307 0.379 0.390 4 100.0 3298.5 2271.1
0.307 0.502 0.490 5 80.0 CuO 2.0 2743.0 956.6 0.611 0.325 0.288
Initial concentration of Mg in melt: 1.31%
DESCRIPTION OF REFERENCE NUMERALS
[0080] G Power generation apparatus [0081] m1 Al alloy melt [0082]
m2 Molten salt [0083] 11 Anode [0084] 21 Cathode [0085] 6 Porous
container body (Separator) [0086] 9 Liquid bath (Container
body)
* * * * *